Rigid polyurethane foams with low thermal conductivities

ABSTRACT

Disclosed are rigid cellular polyurethanes prepared by bringing together under foam forming conditions an aromatic polyisocyanate and a polyhydric combination comprising a major proportion of a crude polyester polyol and minor proportion of a cross-linking polyol. This selection of particular ingredients gives rise to foams having extremely low initial insulation K factor values.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 282,369, filed Dec. 9,1988, now abandoned.

FIELD OF THE INVENTION

This invention relates to the preparation of polymer foams and is moreparticularly concerned with rigid polyurethane foams.

DESCRIPTION OF THE PRIOR ART

Polyurethane foams derived from the reaction of polyisocyanates withboth polyether based polyols and polyester based polyols and mixturesthereof in the presence of blowing agents are well known items ofcommerce. Until recently polyether polyols have been by far the mostwidely used class of polyol resins in the manufacture of rigid cellularpolyurethanes. Primarily, this is due to their low cost and readyavailability. For typical polyether polyols and their commercial sourcessee Plastic Foams Part II pp. 459 to 461 (1973) by K. C. Frisch andJames H. Saunders, Marcel Dekker, Inc., New York, N.Y. 10016. It is onlyrecently that polyester polyols have become of more interest in rigidcellular polyurethane manufacture. This is due to their economicavailability from crude reaction residues and from scrap polyester resinsources.

Generally speaking these newer classes of polyester polyols have beenemployed as so-called extender polyols in combination with polyetherpolyols in order to achieve a proper viscosity mix and fluorocarbonblowing agent solubility in the polyol B side. Also, they have foundapplication in polyisocyanate prepolymer formulations. Typical U.S. Pat.Nos. disclosing such polyester polyols and their application inpolyurethanes are 4,048,104; 4,223,068; 4,400,477; 4,417,001; 4,439,549:4,439,550; 4,442,237; 4,444,918; 4,444,919; 4,465,793: 4,469,821;4,469,824; 4,485,196: 4,506,090; 4,521,611: 4,539,341; 4,544,679:4,559,370; 4,604,410; 4,642,319; 4,644,019: 4,701,477; and 4,722,803.

Of the numerous references cited supra few, if any, disclose theformation of rigid polyurethane cellular materials having exceptionalinsulation properties as evidenced by very low K factors. K factor isthe well-known measure of the insulation property of a cellular materialas typically determined in the units BTU-in/hr. ft² °F. in accordancewith ASTM Test Method C-518. Only U.S. Pat. Nos. 4,539,341 and 4,642,319disclose initial K factors below 0.11. The former reference disclosespolyisocyanurate foams having an initial K factor of 0.107, whereas thepolyurethane foams have initial values of 0.14. The polyisocyanuratefoam was prepared from a polymethylene poly(phenyl isocyanate) and thesubject polyester polyol obtained from polyethylene terephthalate scrapvia digestion with a glycol and a polycarboxylic acid derivative, e.g.phthalic anhydride. Although, the reference teaches the option of using95 to 0 weight percent of other polyols which broadly embrace the totalrange of known organic polyols. In respect of the polyurethane foams,the reference specifically exemplifies blends of the scrap polyesterpolyol with a sucrose/amine polyol in a 30/70 weight blend. The broadteaching is directed to a 5 to 100 percent scrap polyol content butpreferably 20 to 50 percent wherein the complementary polyol is drawnfrom the same broad total range of polyols referred to above.

U.S. Pat. No. 4,642,319 discloses both polyurethane and polyisocyanuratefoams. In this case, the scrap polyester polyol is itself first reactedwith a so-called functionality enhancing agent. Then this polyol productis reacted singly or in combination with (e.g. 0 to 95 weight percent)other polyols with the polyisocyanate. The K factor values for themajority of both the polyurethane and polyisocyanurate foams are greaterthan 0.11. Only a few examples were observed to be significantly below0.11.

U.S. Pat. No. 4,417,001 discloses polyisocyanurate foams made from thepolyisocyanate and a polyol including 5 to 100 percent of a digestionproduct from polyalkylene terephthalate residues and 0 to 95 percent ofa "conventional" polyol. Amongst the conventional polyols there aredisclosed polyols which could be classified as cross-linkers. However,the initial K factors disclosed are not particularly low (i.e. 0.125).

U.S. Pat. No. 4,469,821 also discloses polyisocyanurate foams wherein apreponderance of a crude polyester polyol is used with a minor componentof a particular polyether polyol of average functionality at least 4.Those foams are strictly polyisocyanurate materials and no particular Kfactor data is disclosed.

U.S. Pat. No. 4,604,410 discloses the preparation of rigid polyurethaneor polyisocyanurate foams wherein the polyol component is an etherifiedaromatic polyester polyol derived by digestion of a scrap PET. The scrappolyol may be used alone or in combination with up to 80 parts of apolyoxypropylene polyol. However, no specific polyol blends are shown inthe working examples and the initial K factors measured all exceed 0.11.

In a series of U.S. patents of the same assignee, mixtures of variouslyderived crude polyester polyols are disclosed either for use alone inpreparing polyisocyanurate foams or as extenders with polyether polyolsfor the preparation of polyurethane foams. This series of patentsincludes 4,439,549: 4,439,550; 4,442,237; 4,444,918: 4,444,919:4,469,824; 4,485,196; 4,506,090: and 4,644,019. Generally speaking, inthe case of polyurethanes the polyester component is not used inproportions much above 30 weight percent. Although, in the broadteaching the polyether polyol component is shown to be 0 to 95 percentwith the crude polyester polyol being 100 to 5 percent. The teachingdirected to the polyether polyol component includes conventionalpolyols. Furthermore, none of the working examples in this series ofdisclosures shows an initial K factor below 0.11.

There still remains a need for polyurethane foams which can be preparedfrom readily available polyisocyanates and polyol components and whichfoams possess insulation factors consistently superior to those in theknown art in terms of not being much greater than 0.10. The implicationof having such materials is not only the increase in their insulativecapacity, but also the reduction this leads to in the fluorocarbonblowing agent required. None of the references or teachings referred toabove appears to provide polyurethane foams consistently having initialK factors much below 0.11.

SUMMARY OF THE INVENTION

The present invention is directed to improved rigid cellularpolyurethanes prepared by bringing together under foam formingconditions an aromatic polyisocyanate and a polyhydric combinationcomprising (a) a polyester polyol derived from crude reaction residuesor from scrap polyester resins and (b) a conventional polyol, whereinthe improvement comprises employing as said conventional polyol (b) across-linking polyol in sufficient proportions to result in an initialinsulation K factor of consistently no greater than about 0.106 in saidpolyurethanes.

The rigid cellular polyurethanes of this invention thereby meet the needset forth above for the facile preparation of rigid polyurethane foamshaving improved thermal insulation properties over the known art.

The instant foams are characterized by initial K factor valuesconsistently no greater than 0.106. K factor values "no greater than0.106" does not exclude a value of 0.11 since the error range for thedetermination is plus or minus about 4 percent or approximately 4 unitsin the third place past the decimal (see ASTM C-518 page 158, paragraph13.2). Accordingly, it is not until the third digit exceeds a value ofabout 0.106 that the measured value could be read as being greater than0.11. The preferred foams in accordance with the present invention haveinitial K factor values consistently falling within an incredibly lowrange of from about 0.093 to 0.100.

Notwithstanding the large body of art directed to polyol combinations ofcrude polyester polyols with conventional polyols discussed above, theprior art has not recognized nor provided polyurethane cellularmaterials characterized by such low initial K factors. Quiteunexpectedly, the selection of particular cross-linking polyols andproportions from the prior art to be used in combination with varioustypes of crude polyester polyols, gives rise to the present polyurethanefoams having such surprisingly low initial K factors.

The rigid foams can be employed for all the purposes for which thecurrently produced cellular products are conventionally employed and areparticularly suited for applications where thermal resistance isrequired. For example, the foams can be employed as insulation fortanks, pipes, refrigerator and freezer cabinets and the like.

DETAILED DESCRIPTION OF THE INVENTION

The rigid cellular polyurethanes in accordance with the presentinvention are readily prepared by bringing together the polyisocyanateand polyol combinations under foam forming conditions using any of themixing methods well known in the art. For example, see Saunders andFrisch, Vols. I and II, Polyurethanes Chemistry and Technology, 1962,John Wiley and Sons, New York, N.Y.: more pertinently, see any of theU.S. patents cited supra regarding the use of polyester polyol,polyether polyol combinations for the preparation of polyurethane andpolyisocyanurate foams. In particular, see U.S. Pat. Nos. 4,417,001:4,439,549; 4,439,550: 4,442,237; 4,444,918: 4,444,919; 4,469,821;4,469,824; 4,485,196: 4,506,090; 4,539,341; 4,604,410; 4,642,319: and4,644,019 whose disclosures, relative to the preparation of polyurethanefoams including the aromatic polyisocyanates, crude polyester polyols,foam forming ingredients such as blowing agents, catalysts and otheradjuvants, are incorporated herein by reference. Accordingly, thepolyurethane foams are readily prepared by bringing together the foamforming ingredients either by hand-mix methods for small preparationsand, preferably, machine mixing techniques including high pressureimpingement mixing to form buns, slabs, laminates, pour-in-place,spray-on-foams, froths, reaction injection molded bodies, and the like.

The novelty in the present invention resides in the selection of aparticular class of cross-linking polyols and the selection of theirproportions to be used in combination with the known class of crudepolyester polyols. These selections result in polyurethane foams havinginitial K factor insulation values much lower than heretofore observedwith known polyurethane or polyurethane-polyisocyanurate foams. That theselection invention is even more precise is noted from the fact thatpolyisocyanurate foams made with the identical ingredients, includingtheir respective proportions to each other (except for excesspolyisocyanate) do not have the same low K factors as their polyurethanecounterparts (see examples below).

The term "cross-linking polyol" means a polyol or mixture of polyolswherein the functionality has a value inclusive of an average valuefalling within the range of about 3.5 to about 8, preferably about 4 toabout 6, most preferably about 4 to about 4.5, and a hydroxyl equivalentweight correspondingly falling within the range of about 70 to about230, preferably about 80 to about 180, most preferably about 110 toabout 130.

Particularly useful as a class of cross-linking polyols, are thepolyether polyols resulting from the reaction of an initiator compoundor mixture of initiators with an alkylene oxide or substituted alkyleneoxide or mixtures thereof to provide the polyols having the broad andpreferred functionalities and equivalent weights set forth above.Illustrative of the oxides which can be employed are ethylene oxidepropylene oxide, butylene oxide, epichlorohydrin, epibromohydrin, andmixtures of any of the above.

Illustrative but non-limiting of the initiators are sucrose, glycerine,pentaerythritol, sorbitol, α-methyl glucoside, trimethylolpropane,ethylenediamine, diethylenetriamine, toluenediamine, methylenedianiline,polymethylene poly(phenyl amine), and the like, and mixtures of any ofthe above such that the average functionalities and equivalent weightsfall within the above prescribed ranges. There can also be included inthe polyol mixture difunctional components such as diethanolamine andglycols so long as the overall functionalities and equivalent weightsfall within the prescribed ranges. A preferred cross-linking polyol foruse in the present foams comprises a polyether polyol mixture having anaverage functionality from about 4 to about 6 and equivalent weight fromabout 80 to about 180 obtained from the reaction of ethylene oxide,propylene oxide, or mixtures of ethylene and propylene oxide with acombination of two or more of any of the above initiators and inclusiveof difunctional components.

In respect of the proportions in which the cross-linking polyol is usedin the polyhydric combination, this will .depend somewhat on its overallfunctionality and equivalent weight. It cannot be used as the solepolyol nor can it be used in equal weight proportions with the polyesteras this leads to unacceptably high K factor levels in the resultingfoam. Accordingly, the cross-linking polyol is used in sufficientproportions to result in a polyurethane foam having an initial K factorwhich is consistently no greater than 0.106. The term "consistently" asused in this context means that a majority of the foam samples preparedin accordance with the present invention will have K factors no greaterthan the stated value including the value falling within the range ofexperimental error of this value as explained above. Generally speaking,this material comprises from about 5 to about 40 percent by weight ofsaid polyhydric combination with the complementary portion of 95 to 60percent being the polyester polyol, preferably the cross-linker is fromabout 5 to about 30 percent, and, most preferably from about 10 to about20 percent by weight of the polyhydric mixture.

The crude polyester polyols employed in the polyhydric combination, asthe term "crude" implies, are obtained from crude reaction residues orscrap polyester resins. Generally speaking, they consist of mixtures ofa number of low and high molecular weight hydroxyl containing componentswith their overall or average molecular weights and averagefunctionalities falling within a range of from about 225 to about 5,000and from about 2 to about 6, respectively. Preferably, the averagemolecular weight falls within a range of about 250 to about 1,500 withcorresponding average functionalities of about 2 to about 4. A mostpreferred class of crude polyester polyol has an average molecularweight from about 250 to about 1,000 and average functionality fromabout 2 to about 3.

Those polyester polyol mixtures obtained from crude reaction residuesinclude a number of sources. One such source comprises the polyesterpolyols derived from phthalic anhydride bottoms as disclosed in U.S.Pat. No. 4,521,611 cited supra whose disclosure relative thereto isincorporated herein by reference. A preferred source is best exemplifiedby the mixtures derived from the so-called DMT (dimethyl terephthalate)process residues by transesterification with low molecular weightaliphatic glycols. Typical DMT polyester polyols, for example, aredisclosed in U.S. Pat. No. 3,647,759 which disclosure is incorporatedherein by reference in its entirety and wherein the residue derived fromDMT production via air oxidation of p-xylene is utilized. The oxidateresidue contains a complex mixture of polycarbomethoxy substituteddiphenyls, polyphenyls, and benzylesters of the toluate family. Thisresidue is transesterified with an aliphatic diol such as ethyleneglycol, propylene glycol, diethylene glycol, dipropylene glycol, and thelike to produce a variety of low cost, predominately hydroxyl-functionalpolyester polyols with a wide variety of physical properties. Such DMTderived polyester polyols are produced under the name TERATE® 200 seriesresin polyols supplied by Hercules Inc.

Those polyester polyol mixtures obtained from scrap polyester resins arebest exemplified by the mixtures obtained by digesting scrappolyethylene terephthalate (PET) with low molecular weight aliphaticglycols. Typical are the aromatic ester based polyols derived fromdigesting polyalkylene terephthalate with organic diols and triolshaving a molecular weight from 62 to 500 as disclosed in U.S. Pat. No.4,048,104 which disclosure relative thereto is incorporated herein byreference: the aromatic polyester polyols obtained from the reaction ofpolyethylene terephthalate residue with alkylene oxides in the presenceof a basic catalyst as disclosed in U.S. Pat. No. 4,439,549 alreadyincorporated herein: the aromatic polyester polyols derived fromrecycled polyethylene terephthalate waste streams, alkylene glycols, anddibasic acid waste streams as disclosed in U.S. Pat. No. 4,439,550 andU.S. Pat. No. 4,444,918 which disclosures relative thereto are alreadyincorporated herein; the aromatic polyester polycarbonate polyolsderived from polyethylene terephthalate residues and alkylene carbonatesas disclosed in U.S. Pat. No. 4,465,793 which disclosure relativethereto is incorporated herein by reference: the liquid terephthalicester polyols derived from recycled or scrap polyethylene terephthalateand diethylene glycol and one or more oxyalkylene glycols as disclosedin U.S. Pat. No. 4,469,824 which disclosure relative thereto is alreadyincorporated herein; the polyester polyols made by first reactingrecycled polyethylene terephthalate scrap with an alkylene glycolfollowed by reaction with an alkylene oxide as disclosed in U.S. Pat.No. 4,485,196 which disclosure relative thereto is already incorporatedherein: the copolyester polyols comprising the reaction products of anaromatic component selected from phthalic derivatives, polyethyleneterephthalate, or dimethyl terephthalate with dibasic acid compounds, atleast one primary hydroxyl glycol, and at least small amounts of asecondary hydroxyl glycol as taught in U.S. Pat. No. 4,559,370 whichdisclosure is incorporated herein by reference: and the like.

The polyisocyanate component used in accordance with the presentinvention can be any aromatic polyisocyanate known to be useful in thepreparation of rigid polyurethane foams. Illustrative but non-limitingexamples are m- and p-phenylene diisocyanate, methylenebis(phenylisocyanate), polymethylene poly(phenyl isocyanates), 2,4-,2,6-toluenediisocyanates and mixtures thereof, quasi prepolymers basedon toluene diisocyanates (TDI), dianisidine diisocyanate, bitolylenediisocyanate, naphthalene-1,4-diisocyanate, and the like.

A preferred group of polyisocyanates comprise the polymethylenepoly(phenyl isocyanates), particularly the mixtures containing fromabout 20 to about 85 percent by weight of methylenebis(phenylisocyanate) with the remainder of the mixture comprising polymethylenepoly(phenyl isocyanates) of functionality greater than 2: and mixturesof these polymethylene poly(phenyl isocyanates) with isocyanateterminated quasi prepolymers prepared from 2,4-,2,6-toluenediisocyanates and mixtures thereof with less than 0.5equivalency of at least one polyol component; an even more preferred TDIquasi prepolymer for use in combination with polymethylene poly(phenylisocyanates) is one wherein the TDI reactant is a crude undistilled TDIcontaining a major proportion (70-90 percent) of pure toluenediisocyanate with the residue being phosgenation by-products of thetoluene diamine. This crude TDI can be optionally, partially trimerized(about 10 to 25 percent by weight) prior to reaction with deficientpolyol to form the quasi prepolymer; this is in accordance with thegeneral procedure set forth in U.S. Pat. No. 3,652,424. The proportionsof the two components are not critical but preferably the quasiprepolymer does not exceed about 60 percent by weight of thepolyisocyanate mixture: preferably the mixture comprises 40 to 75percent by weight of polymethylene poly(phenyl isocyanate) with thebalance being the quasi prepolymer.

The proportions of polyisocyanate employed in reaction with thepolyhydric combination are such that the NCO:OH ratio falls within arange of about 0.90 to about 1.15:1, preferably this range is from about0.95:1 to about 1.10:1, most preferably 0.95:1 to 1.05:1.

Any catalyst known in the art for catalyzing urethane formation can beemployed particularly organic amine and organometallic catalysts.Typical but non-limiting examples of organometallic catalysts arestannous octoate, dibutyl tin dilaurate, tin mercaptide, and the like.Typical but not limiting of amines are triethylenediamine,tetramethylethylenediamine, bis(2-dimethylaminoethyl)ether,triethylamine, tripropylamine, tributylamine, triamylamine, pyridine,quinoline, dimethylpiperazine, piperazine, N,N-dimethylcyclohexylamine,N-ethylmorpholine, 2-methylpiperazine, N,N-dimethylethanolamine,tetramethylpropanediamine, methyltriethylenediamine, and the like, andmixtures thereof.

Generally speaking, the quantity of catalyst can fall within a range offrom about 0.001 to about 5 percent by weight of the total polyurethaneforming ingredients. Preferably, the catalyst is most effectivelyemployed within a range of about 0.1 to about 2 percent by weight.

The bringing together of all of the above described ingredients underfoam forming conditions calls for the use of at least one so-calledfoaming agent. Such an agent can be any one of the low boiling organichydrocarbon and halogen substituted hydrocarbons known to be useful forthis purpose. Illustrative of such blowing agents aredichlorodifluoromethane, dichlorofluoromethane,trichloromonofluoromethane, methylene chloride,1,1-dichloro-1-fluoroethane 1,1-dichloro-2,2,2-trifluoroethane,1-chloro-1,1-difluoro-2,2-dichloroethane, 1,1-difluoroethane, C₄ F₈cyclic Freon C-318, and mixtures thereof.

In addition to the above blowing agents, the present formulations alsocontemplate the presence of small proportions of water as additionalblowing agents. Accordingly, water can be present in from zero to about3 parts by weight per 100 parts of polyhydric combination.

The polyurethane foams produced can vary in density from about 0.5 poundper cubic foot to about 40 pounds per cubic foot, preferably from about1.5 to about 6. However, in terms of the most practical densities foruse in insulation applications wherein the uniquely low K factors can berealized to their full effect, the range is from about 1.75 to about 2.2pounds per cubic foot. The density obtained is a factor of how muchblowing agent is employed. The exact proportions of blowing agentrequired for a specific density will depend on the particularformulation being reacted according to such variables, amongst others,as the viscosity of the reaction mixture and the exotherm temperaturesgenerated and the particular agent employed. Accordingly, the necessaryproportions are readily determined by simple trial experiments.Illustratively, the blowing agent will fall within a range of from about5 to about 25 percent, preferably 10 to 20 percent by weight of thetotal formulation weight.

Additional ingredients which may be employed under the foam formingconditions are dispersing agents, cell stabilizers, and surfactants.Surfactants, better known as silicone oils, are added to serve as cellstabilizers. Some representative materials are sold under the names ofSF-1109, L-520, L-521, L-5420, L-5430 and DC-193 which are, generally,polysiloxane polyoxyalkylene block co-polymers, such as those disclosedin U.S. Pat. Nos. 2,834,748: 2,917,480: and 2,846,458, for example. Whenemployed, the surfactant represents from about 0.05 to about 5, and,preferably 0.1 to 2 weight percent of the total ingredient weight

Other optional additives for the foams of the invention can include fromzero to 20, preferably from about 2 to about 15 parts of a flameretardant such as tris(2-chloroethyl)phosphate,tris(2-chloropropyl)phosphate, tris(2,3-dibromopropyl)phosphate,tris(1,3-dichloropropyl)phosphate, diammonium phosphate, varioushalogenated aromatic compounds, antimony oxide, alumina trihydrate,polyvinyl chloride, and the like, and mixtures thereof. Other additivessuch as carbon black, colorants, and the like can be added. The additionof fillers such as barium sulfate may be used in such proportions thatdo not detract from the K factor of the foams.

As noted above, the present polyurethane foams can be provided in a widerange of densities. However, it is within the more generally acceptedrange for thermal insulation applications, i.e. 1.75 to 2.2 p.c.f. thatthe foams enjoy their maximum utility because of their surprisingly lowK factors. It will be noted that it is the initial K factor which isreported herein. One skilled in this art fully recognizes that acellular foam insulation value tends to decrease with time. Accordingly,the present foams are no exception. However, since they start at such alower K value than prior art materials, their insulation value at theend of a measured time period still remains correspondingly lower.

In view of their extremely efficient thermal insulation, the presentfoams find particular utility in the insulation of tanks, pipes, and thelike where either high or low temperatures are to be maintained.Furthermore, the present foams are extremely useful in refrigerator andfreezer cabinets, and the like.

The following examples describe the manner and process of making andusing the invention and set forth the best mode contemplated by theinventors of carrying out the invention but are not to be construed aslimiting.

EXAMPLE 1

The following experiment describes the preparation of eight polyurethanefoams (A through H) in accordance with the present invention and twopolyurethane-polyisocyanurate foams not so in accordance (Comparisons 1and 2).

The foams are prepared by mixing together the ingredients in theproportions of parts by weight set forth in Table I below. The generalprocedure involves first mixing the polyol B component ingredients in a1 gallon plastic tub to be followed by the polyisocyanate A componentingredients. The combined ingredients are then rapidly mixed for 10seconds using a high speed drill press motor (1720 r.p.m.) equipped witha 4 inch diameter Conn agitator. This mixture is immediately poured intoa 14"×14"×14" cardboard box where the resulting foam is allowed to risefreely and the rise profile measurements in seconds recorded as setforth in Table I for each sample. All of the foams are formulated in anisocyanate:hydroxyl ratio of 1.05 except Comparison samples 1 and 2which are classified as polyurethane-polyisocyanurate with the ratio of1.75. Each foam is aged for at least three days at ambient (about 20°C.) room temperature prior to testing for density and the initial Kvalue.

For the foams A through H the highest observed K factor is 0.106 whilethe lowest is 0.096. These values are to be compared with thepolyisocyanurate comparison foams which are beginning to measurablyexceed a value of 0.106.

                                      TABLE I    __________________________________________________________________________                  Foams                                                  Comp.                                                      Comp.    Ingredients (pts. by wt.)                  A   B   C   D   E   F   G   H   1   2    __________________________________________________________________________    Component A    Polyisocyanate I.sup.1                  787.5                      --  --  --  788 --  --  --  1,000                                                      --    Polyisocyanate II.sup.2                  --  770 --  --  --  770 --  --  --  977    Polyisocyanate III.sup.3                  --  --  828 --  --  --  828 --  --  --    Polyisocyanate IV.sup.4                  --  --  --  805.5                                  --  --  --  805.5                                                  --  --    Monofluorotrichloromethane                  100 100 100 100 100 100 100 100 100 100    Component B    Terate ® 203.sup.5                  717 717 717 717 --  --  --  --  547 547    Chardol ® 37-2513.sup.6                  --  --  --  --  695 695 695 695 --  --    Cross-linking polyol I.sup.7                  161 161 161 161 161 161 161 161 122.6                                                      123    L-5420.sup.8  17.6                      17.6                          17.6                              17.6                                  17.1                                      17.1                                          17.1                                              17.1                                                  13.4                                                      13.4    Polycat 8.sup.9                  7.9 7.9 7.9 7.9 7.7 7.7 7.7 7.7 1.34                                                      1.34    Trimer catalyst.sup.10                  --  --  --  --  --  --  --  --  13.4                                                      13.4    Monofluorotrichloromethane                  171 168 178 174 168 165 174 170 172 168    NCO/OH        1.05                      1.05                          1.05                              1.05                                  1.05                                      1.05                                          1.05                                              1.05                                                  1.75                                                      1.75    Properties    Density p.c.f.                  1.92                      1.98                          1.91                              1.93                                  1.97                                      2.11                                          1.91                                              1.91                                                  1.83                                                      1.66    Initial K factor.sup.11                  0.106                      0.100                          0.097                              0.106                                  0.106                                      0.096                                          1.100                                              0.098                                                  0.108                                                      0.116    btu-in/hr. ft.sup.2 °F.    Rise Profile (all in    seconds    Mix           10  10  10  10  10  10  10  10  10  10    Cream         20  14  15  20  15  15  12  15  23  20    Initiation    20  17  17  26  17  16  15  17  26  26    Gel           45  45  40  50  50  43  45  42  58  57    Rise          70  60  60  70  70  53  60  60  74  70    Tack Free     55  65  50  60  90  50  55  55  80  90    Firm          270 155 150 180 180 240 180 180 210 100    __________________________________________________________________________     Footnotes to Table I     .sup.1 Polyisocyanate I: A polymethylene poly(phenyl isocyanate) mixture     comprising about 41 percent by eight of methylenebis(phenyl isocyanate)     with the balance of 59 percent being polymethylene poly(phenyl     isocyanates) of functionality higher than 2; I.E. = about 134; viscosity     about 180 cps (at 25° C.).     .sup.2 Polyisocyanate II: A polymethylene poly(phenyl isocyanate) mixture     comprising about 65 percent by weight of methylenebis(phenyl isocyanate)     with the balance of 35 percent being polymethylene poly(phenyl     isocyanates) of functionality higher than 2; I.E. = about 131; viscosity     about 40 cps (at 25° C.).     .sup.3 Polyisocyanate III: A polymethylene poly(phenyl isocyanate) mixtur     comprising about 23 percent by weight of methylenebis(phenyl isocyanate)     with the balance of 77 percent being polymethylene poly(phenyl     isocyanates) of functionality higher than 2; I.E. = about 141; viscosity     about 1800 cps (at 25° C.)     .sup.4 Polyisocyanate IV: A polymethylene poly(phenyl isocyanate) mixture     comprising about 29 percent by weight of methylenebis(phenyl isocyanate)     with the balance of 71 percent being polymethylene poly(phenyl     isocyanates) of functionality higher than 2; I.E. = about 138; viscosity     about 700 cps (at 25° C.).     .sup.5 Terate ® 203: Transesterified crude DMT residue supplied by     Hercules Chemical Co., Wilmington, Delaware; OH E.W. = 178; functionality     about 2.3; viscosity = about 30,000 cps (25° C.).     .sup.6 Chardol ® 372513: A digestion product from scrap PET reacted     with a mixture of glycols inclusive of diethylene glycol, triethylene     glycol, and phthalic anhydride; OH E.W. = about 165; functionality about     2.3, viscosity = about 13,500 cps (25° C.).     .sup.7 Crosslinking polyol I: Reaction product of a 0.3/1.0 molar mixture     of sucrose and glycerine with 1.2 moles of propylene oxide per hydroxyl     group; E.W. = about 115; average functionality = about 4.3.     .sup.8 L5420: A polydimethylsiloxane polyoxyalkylene block copolymer     surfactant supplied by Union Carbide Corporation.     .sup.9 Polycat 8: A tertiary amine urethane catalyst supplied by Air     Products and Chemicals Inc.     .sup.10 Trimer catalyst: Hexcem 977, a solution of about 75 percent by     weight of potassium octoate and 25 percent diethylene glycol; supplied by     Mooney Chemicals Inc.     .sup.11 K Factor: Measure of heat transfer in BTUinch/hour ft.sup.2     °F., measured in accordance with ASTM Test Method C518.

EXAMPLE 2

This experiment describes the preparation of sixteen polyurethane foams(I through X) in accordance with the present invention and threecomparison foams (3 through 5) not so in accordance. The same procedureand apparatus set forth in Example 1 is used herein along with thevarious ingredients in the proportions of parts by weight set forth inTable II.

This series of foams of the invention differ principally from those ofExample 1 by employing mixtures of the respective polymethylenepoly(phenyl isocyanates) with either a 50/50 or 75/25 weight proportionof a toluene diisocyanate quasi prepolymer identified as TDI quasi I anddescribed in footnote 5 of Table II. This leads to polyurethane foamscharacterized by even lower K factors than those of Example 1. Forexample, foam R has a value of 0.093 and the majority of the foams areconsistently below 0.100.

Comparison foam 3 shows the effect on K factor when one of the otherwisepreferred formulations of the invention is used with excess isocyanateto make a polyurethane-polyisocyanurate foam. A direct comparison ofFoam I with Comparison 3 shows the drop in K factor from 0.096 for theformer to 0.116 for the latter.

Comparison foam 4 shows the effect of employing the cross-linking polyolin too high a proportion in the polyhydric combination. It will be notedthat Foams I through X employ the cross-linking polyol in the 18 to 20percent by weight range with the polyester polyol, whereas Comparison 4employs the cross-linking polyol on a 50/50 weight basis. Its K factorhas the value 0.111 compared with the much lower values for theinvention foams.

Comparison foam 5 shows the effect of using a cross-linking polyol alonein the absence of the polyester polyol ingredient. Its K factor is 0.114which is higher still than Comparison foam 4.

                                      TABLE II    __________________________________________________________________________                  Foams    Ingredients (pts. by wt.)                  I   J   K   L   M   N   O   P   Q   R    __________________________________________________________________________    Component A    Polyisocyanate I.sup.1                  377 --  --  --  578 --  --  --  377 --    Polyisocyanate II.sup.2                  --  372 --  --  --  568.5                                          --  --  --  372    Polyisocyanate III.sup.3                  --  --  387 --  --  --  600 --  --  --    Polyisocyanate IV.sup.4                  --  --  --  381.5                                  --  --  --  588 --  --    TDI Quasi I.sup.5                  377 372 387 381.5                                  193 189.5                                          200 196 377 372    Monofluorotrichloromethane                  100 100 100 100 100 100 100 100 100 100    Component B    Terate ® 203                  717 717 717 717 717 717 717 717 --  --    Chardol ® 37-2513                  --  --   -- --  --  --  --  --  695.1                                                      695    Cross-linking polyol I.sup.6                  161 161 161 161 161 161 161 161 161 161    Cross-linking polyol II.sup.7                  --  --  --  --  --  --  --  --  --  --    L-5420        17.6                      17.6                          17.6                              17.6                                  17.6                                      17.6                                          17.6                                              17.6                                                  17.12                                                      17.12    Polycat 8     6.15                      6.15                          5.3 7.9 6.15                                      6.15                                          7.95                                              7.9 5.1 7.7    Trimer catalyst.sup.8                  --  --  --  --  --  --  --  --  --  --    Monofluorotrichloromethane                  166 164 169 167 168 166 173 167 162 160    NCO/OH        1.05                      1.05                          1.05                              1.05                                  1.05                                      1.05                                          1.05                                              1.05                                                  1.05                                                      1.05    Properties    Density p.c.f.                  1.91                      2.05                          1.93                              2.04                                  1.89                                      1.94                                          1.85                                              1.99                                                  2.02                                                      2.08    Initial K factor                  0.096                      0.094                          0.103                              0.094                                  0.107                                      0.094                                          0.099                                              0.099                                                  0.096                                                      0.093    btu-in/hr. ft.sup.2 °F.    Rise Profile (all in    seconds    Mix           10  10  10  10  10  10  10  10  10  10    Cream         15  15  25  14  22  17  15  14  12  10    Initiation    20  21  30  17  25  21  17  16  15  11    Gel           60  65  80  45  70  55  40  42  60  45    Rise          78  80  120 60  95  65  55  55  75  55    Tack Free     95  100 130 55  110 80  50  50  95  50    Firm          210 240 240 240 220 240 180 240 180 300    __________________________________________________________________________                  Foams                                             Comp.                                                 Comp.                                                      Comp.    Ingredients (pts. by wt.)                  S   T    U   V    W   X    3   4    5    __________________________________________________________________________    Component A    Polyisocyanate I.sup.1                  --  --   578 --   --  --   478 377  377    Polyisocyanate II.sup.2                  --  --   --  568.5                                    --  --   --  --   --    Polyisocyanate III.sup.3                  387 --   --  --   600 --   --  --   --    Polyisocyanate IV.sup.4                  --  381.5                           --  --   --  588  --  --   --    TDI Quasi I.sup.5                  387 381.5                           193 189.5                                    200 196  478 377  377    Monofluorotrichloromethane                  100 100  100 100  100 100  100 100  100    Component B    Terate ® 203                  --  --   --  --   --  --   547 --   --    Chardol ® 37-2513                  695 695  695 695  695 695  --  380  --    Cross-linking polyol I.sup.6                  161 161  161 161  161 161  123 380  --    Cross-linking polyol II.sup.7                  --  --   --  --   --  --   --  --   753    L-5420        17.12                      17.12                           17.12                               17.12                                    17.12                                        17.12                                             13.4                                                 15.2 15.1    Polycat 8     4.3 7.7  6.15                               7.7  7.7 7.7  1.34                                                 5.3  11.3    Trimer catalyst.sup.8                  --  --   --  --   --  --   6.7 --   --    Monofluorotrichloromethane                  165 164  165 163  170 167  165 146  166    NCO/OH        1.05                      1.05 1.05                               1.05 1.05                                        1.05 1.75                                                 1.05 1.05    Properties    Density p.c.f.                  1.93                      1.96 2.06                               2.09 1.98                                        2.01 1.80                                                 1.85 1.83    Initial K factor                  0.103                      0.094                           0.099                               0.096                                    0.101                                        0.096                                             0.116                                                 0.111                                                      0.114    btu-in/hr. ft.sup.2 °F.    Rise Profile (all in    seconds    Mix           10  10   10  10   10  10   10  10   10    Cream         22  9    18  10   8   12   25  20   10    Initiation    25  10   20  12   10  15   30  22   10    Gel           80  40   78  45   45  45   80  85   60    Rise          115 60   90  55   55  60   100 120  85    Tack Free     145 55   130 60   50  60   130 130  100    Firm          240 240  240 300  180 240  240 300  360    __________________________________________________________________________     Footnotes to Table II     .sup.1-4 Polyisocyanates I to IV: These are the same polyisocyanates     described in Footnotes 1 to 4 of Table I.     .sup.5 TDI Quasi I: A quasi prepolymer having an isocyanate eq. wt. =     about 122.5 and functionality = about 2.15 and viscosity = about 600 cps     (at 25° C.) obtained by reacting (1) about a 7 percent by weight     proportion of a polyether polyol obtained by propoxylating a     sucrose/glycerine mixture to a product of equivalent wt. = about 126,     functionality = about 4.5, and viscosity = about 6,500 cps (at 25°     C.); with (2) about 93 percent by weight of#  a partially trimerized crud     toluene diisocyanate obtained by trimerizing a crude TDI mixture of about     85 to about 87 percent pure toluene diisocyanate and about 15 to about 13     percent of crude toluene diisocyanate phosgenation byproducts to a trimer     content of about 17 percent by weight; this quasi prepolymer is obtained     essentially in accordance with the procedures set forth in U.S. Pat. No.     3,652,424.     .sup.6 Crosslinking polyol I: described in footnote 7 of Table I.     .sup.7 Crosslinking polyol II: Blend of (1) about 77 percent by weight of     a propoxylated mixture of sucrose and an already propoxylated blend of     sucrose/glycerine (described as crosslinking polyol I in Table I) to an     eq. wt. = about 152 and functionality about 7; (2) about 13 percent by     weight methyldiethanolamine; and (3) about 10 percent of a 2,000 molecula     weight polypropylene glycol; blend eq. wt. = about 130; and average     functionality = about 4.0.     .sup.8 Trimer catalyst: described in footnote 10 of Table I.

EXAMPLE 3

This experiment describes the preparation of four polyurethane foams (Y,Z, Y-1, and Z-1) all in accordance with the present invention. The sameprocedure and apparatus set forth in the previous examples is employedherein along with the ingredients in the proportions of parts by weightset forth in Table III.

This series of foams differs principally from those of Example 2 inemploying the Polyisocyanate I with a TDI Quasi II prepolymer differingfrom that employed in previous examples and described in footnote 2below. The polyisocyanate mixtures are employed either in a 50/50 or75/25 weight combination with the same polyester polyols andcross-linking polyol I previously employed in the above examples

All of the foams are characterized by the low K factors characteristicof the present foams except for Y-1 which has a value of 0 114. Thisvalue is considered to be not representative because the actual foamsample is poor with large voids Selection of a proper foam sample for Kfactor testing is not possible

                  TABLE III    ______________________________________                   Foams    Ingredients (pts. by wt.)                     Y       Y-1*    Z     Z-1    ______________________________________    Component A    Polyisocyanate I.sup.1                     377     578     377   578    TDI Quasi II.sup.2                     377     193     377   193    Monofluorotrichloromethane                     100     100     100   100    Component B    Terate 203       717     717     --    --    Chardol 37-2513  --      --      695   695    Cross-linking polyol I.sup.3                     161     161     161   161    L-5420           17.6    17.6    17.12 17.12    Polycat 8        6.15    6.15    5.1   6.15    Monofluorotrichloromethane                     166     168     1.62  165    NCO/OH           1.05    1.05    1.05  1.05    Properties    Density, pcf     1.98    2.04    2.15  1.89    Initial K factor 0.100   0.114   0.099 0.104    btu-in/hr. ft..sup.2 °F.    Rise profile (all in seconds)    Mix              10      10      10    10    Cream            20      25      17    15    Initiation       22      28      20    20    Gel              65      70      70    65    Rise             90      90      100   75    Tack free        120     130     155   125    Firm             240     190     240   180    ______________________________________     *Large voids in the foam due to improper mixing thereby yielding poor foa     samples and thus the high K factor value.     Footnotes to Table III      .sup.1 Polyisocyanate I: described in footnote 1 of Table I.     .sup.2 TDI Quasi II: A quasi prepolymer having an isocyanate eq. wt. =     about 122 and functionality = about 2.1 and viscosity = about 150 cps (at     25° C.) obtained by reacting a mixture comprising (1) about 93     percent by weight of crude undistilled toluene diisocyanate containing     about 75 percent by weight of pure toluene diisocyanate and 25 percent     crude toluene diisocyanate phosgenation byproducts; (2) about 4 percent b     weight of a propoxylated sucrose/glycerine:# 64/36 by wt. mixture to     functionality of about 4.5, eq. wt. = about 126; and (3) about 3 percent     of dipropylene glycol.     .sup.3 Crosslinking polyol I: described in footnote 7 of Table I.

What is claimed is:
 1. In a rigid cellular polyurethane prepared bybringing together under foam forming conditions an aromaticpolyisocyanate and a polyhydric combination comprising (a) a polyesterpolyol derived from crude reaction residues or from scrap polyesterresins and (b) a conventional polyol, the improvement which comprisesemploying as said conventional polyol (b) from about 5 to about 30percent by weight based on the combined weight of (a) and (b) of across-linking polyether polyol to result in an initial insulation Kfactor of consistently about 0.093 to about 0.100 btu-in/hr. ft² °F. insaid polyurethane.
 2. A rigid cellular polyurethane according to claim 1wherein said cross-linking polyol (b) has a functionality from about 3.5to about 8 and equivalent weight from about 70 to about
 230. 3. A rigidcellular polyurethane according to claim 1 wherein said polyester polyol(a) has an average functionality from about 2 to about 4 and averagemolecular weight from about 250 to about 1,500.
 4. A rigid cellularpolyurethane according to claim 1 wherein said polyester polyol isderived from a crude reaction residue.
 5. A rigid cellular polyurethaneaccording to claim 1 wherein said polyester polyol is derived from scrappolyester resins.
 6. A rigid cellular polyurethane according to claim 1wherein said polyisocyanate is selected from the group consisting ofpolymethylene poly(phenyl isocyanates) and mixtures thereof with toluenediisocyanate quasi prepolymers.
 7. A rigid cellular polyurethaneaccording to claim 1 wherein the overall proportions of polyisocyanateto polyhydric combination are such that the NCO:OH ratio falls within arange of about 0.90 to 1.15:1.
 8. A rigid cellular polyurethanecharacterized by an initial K factor of consistently about 0.093 toabout 0.100 btu-in/hr. ft² °F. which comprises the reaction productobtained by bringing together:I. a polyisocyanate selected from thegroup consisting of polymethylene poly(phenyl isocyanates) and mixturesthereof with toluene diisocyanate quasi prepolymers; II. a polyhydriccombination comprising:(a) from about 95 to about 70 percent by weightof a polyester polyol derived from crude reaction residues or from scrappolyester resins said polyester polyol having an average functionalityfrom about 2 to about 4 and average molecular weight from about 250 toabout 1,500; and (b) from about 5 to about 30 percent of a cross-linkingpolyol having a functionality from about 3.5 to about 8 and equivalentweight from about 70 to about 230; III. A urethane catalyst; and IV. ablowing agent.
 9. A rigid cellular polyurethane according to claim 8wherein said (II) comprises (a) from about 80 to about 90 percent byweight of a polyester polyol derived from a dimethyl terephthalate (DMT)process residue by transesterification with low molecular weightaliphatic glycols; and (b) from about 20 to about 10 percent of apolyether polyol mixture having an average functionality of about 4 toabout 4.5 and equivalent weight of about 110 to about
 130. 10. A rigidcellular polyurethane according to claim 9 wherein said (I) comprises apolymethylene poly(phenyl isocyanate).
 11. A rigid cellular polyurethaneaccording to claim 9 wherein said (I) comprises a mixture of (i)polymethylene poly(phenyl isocyanate) and (ii) an isocyanate terminatedquasi prepolymer prepared from the reaction of a crude toluenediisocyanate, optionally, partially trimerized, with at least oneorganic polyol
 12. A rigid cellular polyurethane according to claim 11wherein said (I) comprises from about 40 to about 75 percent by weightof (i) and 60 to 25 percent (ii).
 13. A rigid cellular polyurethaneaccording to claim 8 wherein said (II) comprises (a) from about 80 toabout 90 percent by weight of a polyester polyol derived from a scrapPET by digestion with at least one low molecular weight aliphaticglycol: and (b) from about 20 to about 10 percent of a polyether polyolmixture having an average functionality of about 4 to about 4.5 andequivalent weight of about 110 to about
 130. 14. A rigid cellularpolyurethane according to claim 13 wherein said (I) comprises apolymethylene poly(phenyl isocyanate).
 15. A rigid cellular polyurethaneaccording to claim 13 wherein said (I) comprises a mixture of (i)polymethylene poly(phenyl isocyanate) and (ii) an isocyanate terminatedquasi prepolymer prepared from the reaction of a crude toluenediisocyanate, optionally, partially trimerized, with at least oneorganic polyol.
 16. A rigid cellular polyurethane according to claim 15wherein said (I) comprises from about 40 to about 75 percent by weightof (i) and 60 to 25 percent (ii).
 17. In a rigid cellular polyurethaneprepared by bringing together under foam forming conditions an aromaticpolyisocyanate and a polyhydric combination comprising (a) a polyesterpolyol derived from crude reaction residues or from scrap polyesterresins and (b) a conventional polyol, the improvement which comprisesemploying as said conventional polyol (b) from about 5 to 30 percent byweight based on the combined weight of (a) and (b) of a cross-linkingpolyether polyol which is the reaction product of an alkylene oxide ormixture thereof and an initiator selected from the group consisting ofsucrose, glycerine, pentaerythritol, sorbitol, α-methyl glucoside,trimethylolpropane, ethylenediamine, diethylenetriamine, toluenediamine,methylenedianiline, polymethylene poly(phenyl amine) and mixturesthereof, to result in an initial insulation K factor of consistentlyabout 0.093 to 0.100 btu-in/hr. ft² °F. in said polyurethane.
 18. Arigid cellular polyurethane characterized by an initial K factorconsistently about 0.093 to 0.100 btu-in/hr. ft² °F. which comprises thereaction product obtained by bringing together:I. a polyisocyanateselected from the group consisting of poymethylene poly(phenylisocyanates) and mixtures thereof with toluene diisocyanate quasiprepolymers; II. a polyhydric combination comprising:(a) from about 95to about 70 percent by weight of a polyester polyol derived from crudereaction residues or from scrap polyester resins said polyester polyolhaving an average functionality from about 2 to about 4 and averagemolecular weight from about 250 to about 1,500; and (b) from about 5 toabout 30 percent of a crosslinking polyester polyol having afunctionality about 3.5 to about 8 and equivalent weight from about 70to about 230, which polyether polyol is the reaction product of analkylene oxide or mixture thereof and an initiator selected from thegroup consisting of sucrose, glycerine, pentaerythritol, sorbitol,α-methyl glucoside, trimethylolpropane, ethylenediamine,diethylenetriamine, toluenediamine, methylenedianiline, polymethylenepoly(phenyl amine) and mixtures thereof; III. a urethane catalyst; andIV. a blowing agent,wherein the overall proportions of (I) and (II) aresuch that the NCO:OH ratio falls within a range of about 0.90 to 1.15:1.